Prevent duplicate ML Kit barcode-scanning AAR packaging

[Copilot]

Fixes #1519.

Xamarin.Google.MLKit.BarcodeScanning must continue using Xamarin.Build.Download because the ML Kit AAR is distributed under license terms that prevent embedding it directly in the NuGet package.

The generated package currently exposes the same barcode-scanning AAR through three registrations:

1. The local AAR is packed into lib/ by the binding project.
2. Xamarin.Build.Download downloads the licensed AAR once at build time.
3. The downloaded path is registered twice as XamarinBuildDownloadAndroidAarLibrary by the targets template.

The duplicate XBD items do not download the AAR twice; they add the same downloaded file to AndroidAarLibrary twice. Together with the embedded copy, this produces duplicate XA4301 native-library warnings for consumers.

This change:

• Sets Pack="false" on the local XBD AndroidLibrary, keeping it available for binding generation without embedding it in the NuGet package.
• Removes the duplicate XamarinBuildDownloadAndroidAarLibrary declaration while retaining one required declaration, so the licensed AAR is still downloaded and included exactly once for consumers.
• Removes the obsolete pre-XBD-0.10 compatibility comment; the project pins Xamarin.Build.Download 0.11.4.
• Bumps Xamarin.Google.MLKit.BarcodeScanning from 117.3.0.8 to 117.3.0.9.

The resulting package preserves the license-driven XBD flow and eliminates both sources of duplicate AAR inclusion.

[Copilot]

Pull request overview

This pull request updates the Xamarin Build Download (XBD) packaging flow for Xamarin.Google.MLKit.BarcodeScanning to avoid embedding the same ML Kit barcode-scanning AAR that is also restored via build-transitive download targets, eliminating duplicated-native-library (XA4301) warnings for consumers.

Changes:

• Prevent packing of local XBD AAR inputs by marking the AndroidLibrary item as Pack="false" in the XBD project template.
• Remove a duplicate XamarinBuildDownloadAndroidAarLibrary item emission in the XBD targets template so the downloaded AAR is only included once.
• Bump Xamarin.Google.MLKit.BarcodeScanning NuGet version from 117.3.0.8 to 117.3.0.9.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
source/XamarinBuildDownloadTargets.cshtml	Adjusts generated build-transitive targets to avoid duplicating the downloaded AAR library item.
source/_XBDProjectType.cshtml	Ensures local AAR inputs don’t get packed into the NuGet, avoiding embedding + download duplication.
config.json	Version bump for Xamarin.Google.MLKit.BarcodeScanning to ship the packaging fix.

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[jonathanpeppers]

@dalexsoto review

[dalexsoto]

The local licensed AAR remains available for binding but is excluded from the package, the XBD-downloaded AAR is registered exactly once, and package 117.3.0.9 builds and validates without duplicate XA4301 warnings.